This invention is directed to a telecommunication system in which a plurality of synchronous channels are utilized to support corresponding telephone calls and where the synchronous transmission channels are coupled to an asynchronous communication module. More specifically, this invention addresses minimizing the queuing or delay problems associated with providing a synchronous-to-asynchronous interface.
A conventional telecommunication system may utilize a switch such as an AT&T 5ESS.RTM. switch consisting of an administrative module, a communications module, and switching modules which support a plurality of telephone subscribers. The switch modules and the communications module each provide synchronous communication channels in which an originating and a terminating subscriber are assigned respective channels (time slots) by which information, such as voice, facsimile, data encoded at 64 Kbps, is transmitted between the subscribers. Since the communications module and the switch modules all use synchronous communication channels, delays associated with storing information in queue are not encountered; each communication path has a pre-assigned time slot in both the communications module and the associated switch modules.
Asynchronous data communication systems such as those using asynchronous packets to carry information provide an alternative to the synchronous communication systems typically utilized for voice communications. Asynchronous communication systems do not have an assigned time slot; instead, asynchronous packets carry the subscriber's conversation. It is possible that a plurality of packets destined for the same node in the asynchronous system may result in the need to buffer or store a predetermined number of packets for delivery to the node. This situation exists where two or more packets concurrently arrive at node. The depth or number of packets which are stored leads to an increased delay for packets traversing such a system. Such timing delays may be significant in certain applications such as when voice or other time critical communications are carried. For example, other equipment associated with the system such as synchronous equipment may have time requirements which limit the maximum allowable delay which can be tolerated to achieve acceptable performance. Thus, there exists a need where synchronous and asynchronous systems are both utilized to carry a telephone call to minimize queuing delays associated with the asynchronous system.